High-Stress Magnetic Recording Disks for Shock Deflection Control
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Solution Overview
Problem
Magnetic recording disks in multi-platter hard disk drives (HDDs) face deflection issues due to mechanical shocks, which can exceed the gap between the disk edge and the load-unload ramp, causing damage, and increasing thickness is not feasible due to form factor constraints.
Innovation Solution
The disks are designed with a thickness of 0.5 mm or less and an internal stress of 300 MPa or greater, with a stress-to-thickness ratio in the range of 0.96 to 1.44 GPa/mm², achieved through materials like aluminum-magnesium alloy and glass substrates, and deposition processes, to enhance rigidity and reduce deflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If disk thickness is increased to reduce deflection from mechanical shocks, then disk rigidity is improved, but the overall HDD size exceeds form factor specifications
Solution Approach 1:
The patent introduces internal stress as a new parameter to control disk rigidity. By inducing high internal stress (≥300 MPa) in thin disks through controlled deformation during manufacturing, the disk achieves enhanced rigidity without increasing thickness, thereby maintaining compact HDD form factor while resisting mechanical shock-induced deflections
Solution Approach 2:
The patent employs composite disk structures with multiple layers including substrate, buffer layers, and magnetic recording layers. This composite construction allows optimization of mechanical properties through material selection and layer configuration, achieving high rigidity in thin disks without exceeding size constraints
2Volume of moving object
If disk thickness is decreased to meet form factor specifications, then HDD size is reduced, but disk rigidity decreases making it susceptible to shock-induced deflection
Solution Approach 1:
The patent transforms the rigidity problem by changing from geometric parameters (thickness) to material parameters (internal stress). Thin disks are manufactured with controlled internal stress states that provide shock resistance equivalent to much thicker disks, enabling compact HDD design without sacrificing mechanical durability
Solution Approach 2:
The patent applies preliminary stress treatment during disk manufacturing before the disk is installed in the HDD. By pre-inducing controlled deformation and stress in the thin disk substrate, the disk is prepared in advance to resist mechanical shocks, compensating for the lack of thickness-based rigidity
Data Source
AI summary
Disks for use in hard disk drives (HDD) or other magnetic recording apparatus. The disks are configured based on a finding that internal stress within a disk can make the disk more resistant to shock forces. In one example, a disk is provided that has a substrate with a thickness of no more than 0.5 millimeters and an internal stress no less than 300 megapascals. The relatively high internal stress within the substrate of the disk serves to reduce the magnitude of deflections caused by mechanical shocks to an HDD in which the disk is installed, as compared to other disks of equal thickness but with relatively less internal stress. Multi-platter stacks of the disks are described. Methods are also described for fabricating such disks and for rejecting disks that do not meet certain internal stress-based criteria. Substrates are also described.